Vol. 6, No. 10, Octoher 1967
AZIDOCFILOROBIS(ETHYLENEDIAMINE)COBALT(~~~) ION IS07
rate of water exchange of [Co(en)zOH(HzO)]2+compared to p - [ C ~ ( t r i e n ) O H ( H ~ O ) ]or ~ +from , a combination of these factors.
Acknowledgment.-This work was supported in part by the National Institutes of Health under Grant GM 0835 0.
CONTRIBUTION FROM THE RESEARCH SCHOOL OF CHEMISTRY, AUSTRALIANNATIONAL UNIVERSITY, CANBERRA, AUSTRALIA
The Induced Aquation Reactions of the Resolved Azidochlorobis(ethyl6nediamine)cobal t (I 11) Ion BY D. A. BUCKINGHAM, I. I. OLSEN, AND A. M. SARGESON
Received M u y 2, 1967 The induced aquation of C1- and N3- from ( + ) K W [ C O ( ~ ~ ) Z C+I using N ~ ] Hg2+ and NO+, respectively, has been examined. Both reactions give substantial rearrangement to both cis and tmns products whereas the spontaneous aquation of C1- gave full retention of the cis configuration and activity. The results are compared with the NO+-assisted aquation of [Co(en)z(N3)~] + and the Hgz+-assisted aquation of (-I- )w- [Co(en)zClz]+ where the same products are produced. A common result was obtained for the t w o sets of reactions which is interpreted to indicate a common intermediate.
The present work is related to this last study and Introduction primarily the steric course of the Hg2+-assisted The steric courses of aquation of [ C O ( ~ ~ ) ~ X Y involves ]~+ aquation of C1-, the NO+-assisted aquation of N3-, complexes (where X and Y are a series of substituents and the spontaneous aquation of C1- in the (+)-Cosuch as C1, Br, NCS, "3, OHz, N3, NOz, etc.) have (en)&1N3]+ ion. been well studied,' and i t is still not clear if these reactions proceed by a bimolecular displacement reaction Experimental Section or through an intermediate of reduced coordination (+)58g-~is-[C~(en)(Na)~] c104 was prepared as described.9 number. Attempts have been made to generate the Anal. Calcd: C, 13.25; H, 4.45; N, 38.63. Found: C, possible five-coordinate intermediates involved,2--4 to 13.38; H, 4.55; N, 38.98. trans-[Co(en)~(Na)z] C104 was prepared by the same method as study their properties, and to see if the steric course for cis-[Co(en)z(I%)~] ClO4 using CO(c104)z and HClO4 instead of of the reaction of the supposed intermediate coincides A yield of 87y0 brown truns-[Co(en)zCo(N03)~and "01. with that of the spontaneous aquation. The methods (Na)z]C104 was obtained. Anal. Calcd: C, 13.25; H, 4.45; N, used have been derived from studies of induced aqua38.63. Found: C, 13.44; H, 4.50; N,38.90. tions in substituted cobalt(II1) pentaammine comtr~ns-[Co(en)~N~Cl] C104 was prepared from t r ~ n s - [ C o ( e n ) ~ ( N ~ ) zC104 ] as described.1° plexes, namely, the reactions of [Co(NH3)5XI2+ions C1 was prepared by treating cis- [Co(en),(X = C1, Br, I) with H g 2 + 5and of [ C O ( N H ~ ) ~ N ~ ] ~cis-[Co(en)~NaCl] + (20 (N~)z]NO ~ g) with HCl (10 N ) saturated with LiCl (75 ml) with Evidence has been collected5-* to support a t room temperature until the solution became bluish red (-6 the existence of a common five-coordinate intermediate min). The azidochloro complex was then precipitated by pourin the induced aquations and these reactions have also ing the reaction mixture into a large amount of ethanol. It was recrystallized from water a t p H 3-4 by adding ethanol until prebeen used with cis- and trans- [ C ~ ( e n ) ~ C l ~[Co(en)z]+,~ cipitation commenced. The solution was then cooled in an ice (N3)2]+ 1 3 lCo(en)zOHzN3] z + , 3 [Co(en)~ClOH2]~+,~ [Cobath, yield 5 g. (en)zBrOHz]2 +, [ c o (en)zCIBr]+, and trans- [Co(en)2(+)ssg-cis-[Co(en)~N~C1]CIOn.-To cis-[Co(enjzC1N3]C1 (7.5 g) ClN3]+ ions, t o show that the steric courses of the dissolved in water (80 ml) a t pH 3-4 was added (-)hsg-Na[Coinduced aquation and the spontaneous aquations differ. ( e n ) ( C ~ 0 4 )" ~2 ]0 (4.1g) with stirring. The diastereoisomer (4.4 g) precipitated rapidly and was collected and washed with ice-cold Loeliger and Taube have tabulated data4for the Hg2+water and methanol. The isomer (+)rsg-cis-[Co(en)~NsCl]I and NO+-induced aquations to show that for the same (2.4 g ) was obtained from the diastereoisomer by grinding an iceproduct a constant ratio of cis and trans isomers is obcold suspension of the latter with solid NaI in a mortar. The tained from different reactants. The authors suggest precipitated iodide was collected and washed with a dilute aquethat the common result indicates the same intermediate ous solution of NaI and ethanol. The rotation of the iodide was measured, and, in order to ensure that optical purity was obis formed in the reactions. (1) C. K. Ingold, R. S . Nyholm, and M. L. Tobe, Natuve, 187, 477 (1960). (2) A. M. Sargeson, Austvaliaiz J . Chem., 17, 385 (1964). (3) D. A. Loeliger and H. Taube, Inovg. Chem., 4, 1032 (1965). (4) D. A. Loeliger and H Taube, ibid., 5 , 1376 (1966). (5) F. A. Posey and H. Taube, J . A m . Chem. Soc., 79, 255 (1957). (6) A. Haim and H. Taube, Inoug. Chem., 2, 1199 (1963). (7) D. A. Buckingham, I. I. Olsen, A. M. Sargeson, and H. Satrapa, i b i d . , 6 , 1027 (1967). (8) D. A. Buckingham, I. I. Olsen, and A. M. Sargeson, Auslrnlion J . Chem., 20, 897 (1967).
tained, the complex was reresolved. The iodide was converted to the chloride by treating an aqueous suspension (pH 3 ) with AgCl. After filtration, solid ( - )ss~-Na[Co(en)(CzO&](1.83 g) was added to the filtrate and the diastereoisomer collected was converted to the iodide as before. The final rotation of the iodide was the same as that obtained from the first diastereo(9) P. J. Staples and M. L. Tobe, J . Chem. Soc., 4812 (1960). (10) D. A. Loeliger and H. Taube, Inorg. Chem., 6, 1376 (1906).
1808 D. A. BUCKINGHAM, I. I. OLSEN,
AND
A. kf.SARGESON
isomer. (For a 0.025y0 solution in M HC104 01 is -0.144' a t 520 mp and 20" in a 1-dni tube.) The complex iodide was then converted to the perchlorate by treating it with an aqueous suspension of AgCl followed by excess KaC104. Two fractions were obtained of which the first one contained a small amount of diazido complex. The pure perchlorate gave [a:Zodao -608" (for a 0.0257, solution in d l HClO4 N is -0.152' a t 520 mM and 20') and [ N ] ~ ~ S +240". ~ O Anal. Calcd for (+)jge[C0(en)~N~Cl]C1S 0 ~, :27.54; C, 13.49; H, 4.52. Found: 5 , 27.67; C, 13.67; H , 4.45. The purity of the complex was also tested by thin layer chromatography on cellulose." The components of a mixture of cis-[Co(eii)2(Sa)2]C101 and cis\Co(en)?Cl2]( 2 1 0 4 readily separated by elution with a mixture of 1-butanol (H20 saturated)-HC104 (100:3), and the azidochloro complex moved as a single band between the diazido and dichloro reference samples. cis-[Co(en)2(H20)N3]S04.H20.-cis-[Co(en)2X:3C1] C1 (3 g ) dissolved in 1 iM H?S04 (10 ml) was treated with an aqueous solution of mercuric acetate (3.2 g). After the reaction was complete, a large amount of ethanol was added to precipitate the products. The precipitate was extracted with water and the dark red residue was collected. This was dissolved in very dilute acetic acid and methanol was added to incipient precipitation. The compound was recrystallized by this method until a constant absorption spectrum was obtained ( t j 0 8 300). Anal. Calcd: C, 13.60; H , 5.70; N, 27.76. Found: C, 13.84; H, 5.54; N, 27.86. t~ans-[Co(en)~(H~O)N~]S0~.2H~O.--A suspension of trans[Co(en)2K;sCl]ClOa(2.1 g ) in 1 J l H2S04 (6 ml) was treated with mercuric acetate (0.95 g) dissolved in water. When the violet complex had dissolved and had become bluish red, the solution was filtered and poured into ethanol where the aquoazido compound precipitated. I t was recrystallized by dissolution in cold sulfuric acid (10- Ar) and by adding ethanol until precipitation started. Anal. Calcd: C, 12.94; H , 5.97; S , 26.42. Found: C, 13.59; H , 5.95; AT, 26.14. (+)jss-[Co(en)2C12]C104.-[Co(en)d212] C1 was resolved as described previously,2 except that the (+)jgg-[Co(en)2Cl?]I isolated was resolved twice more by the same procedure to guarantee its optical purity. Anal. Calcd for (+)ass-[Co(en)&12]'2104: C, 13.74; H, 4.61; ?;, 16.03. Found: C, 13.82; H , 4.74; S , 15.99. The Hg*+-induced aquation of [Co(en)eClz]Clod was also carried out as described p r e v i ~ u s l y ,except ~ that the optical density was measured more accurately with a Cary 14 spectrophotometer and the rotations were measured with a Perkin-Elmer 141 spectropolarimeter (10.002 "). Successive experiments gave optical densities of 0.364 and 0.362 a t 518 mp, compared with 0.34 =t0.01 observed previously2 using a Shimadzu RS27 spectrophotometer. The first values correspond to 76% cis- and 24% trans-chloroaquo product (+2%, obtained using the molar absorptivities recorded in ref 2 ) . The corresponding rotations of the carbonato complex formed from these solutions were +l.780° and +1.790" which correspond with 78 i. 1% D-cis[Co(en)sClOH]z+. In order to ensure that no isomerization or racemization of (-)~~~-[Co(en)2Cl~]C104 took place catalyzed by Hg2+ ions, the complex (0.035 g ) was dissolved in HClOl (10 ml, 0.1 N ) a t 20" and Hg(C1O4)*(2.5 ml of 1 0 P iz/i HgO in 0.1 N HC104) was added. After 5 min, the solution was transferred to an ion-exchange column (Bio-Rad analytical resin Dowex (H+) 50W-X2 200-400 mesh 15 X 120 mm) and the mixture was eluted a t 0' with 1 M KaC104 (pH 3). An appropriate volume of eluent containing cis-[Co(en)2Clz] was collected and the absorption ( 0 5 3 6 0.430 -0.174') were measured. in a 5-cm cell) and optical rotation The spectrum and rotation of optically pure (- )j8~[Co(en)2C12]c l o d in 1 NaC1O4 (pH 3 ) gave [ & f I z 0 ~ - 1868" and t 6 3 5 91.8, from which the molar rotation of the unreacted ( - ) w [Co(en)2Clz]+ion was calculated as [M]*OD - 1858'. Kinetic Studies.-The rate data were obtained conductometrically, spectrophotometrically, and polarimetrically using a +
(11) S. Harriiing a n d C. R. SchXffer, privnte commiinirnlion.
Inorganic Chemistry
Wayne-Kerr B221 universal bridge, a Cary 14 spectrophotometer, and a Perkin-Elmer 141 spectropolarimeter, respectively. The nitrous acid induced aquations were performed by dissolving the complex (0.01 g ) in HCIO4 (40 ml, 0.1 Jl)a t 20" and adding NaPiOa immediately after dissolution. T o form the [Co(en)2(H2O)S3l2+products 1 equiv of NaNOz was added to cis-[Co(en)?(Ns)?]Clod; in the other nitrosations a 10% excess was used. After 5 min the rotatory dispersion and absorption spectra were recorded. Then an excess of solid SaHCOa was added to the reaction mixture and the solution was allowed to stand for 15 min before the optical activity of the formed carbonato complex was measured a t the Na D line. In the mcrcuric ion assisted reactions cis- [Co(en)2NsCl]C10, (0.01 g ) WAS dissolved in HC104 (20 ml, 0.1 M ) and the Hg2+ solution (20 ml of 0.01 M HgO in 0.1 M HC10a) was added. The visible absorption spectrum of the aquoazido complexes was measured after 5 min and followed by the addition of a l0yo excess of NaXO:!. After a further 5 min the spectrum of the mixture of diaquo complexes was obtained and finally addition of SaHCOB in excess gave the [Co(en)zCOs]-' ion. cis-[Co(en)pNaOH?]SOq. H20 (0.01 g in 40 ml of 0.1 M HC104) was treated with ZOyo excess of solid KaSOz a t 20' and the visible spectrum was measured after 5 min (€492 80.7). The spontaneous aquation of (+ ):,~e-cis-[Co(en)2iY3C1] C104 was followed by dissolving the complex (0.01 g ) in 0.1 and 0.01 JVf HC104 (40 mlj a t 25' and allowing the solutions to stand for 3.75 and 4.5 hr, respectively. The reaction mixtures were then treated with 10% excess of solid XaN02. After 5 tnin, SaHCO:) was added and the rotations of the formed carbonato complexes were measured a t the Xa D line. Isomerization of czs-[Co(en)2M ) was followed spectrophoto(HzO)Na]SOd.Hz0 (0.7 X metrically a t 25" in 0.01 N HC104.
Results The visible absorption spectra of cis-[Co(en)2C1Na] + and cis- and truns-[C0(en)~N3H~O]~+ ions are given in Figure 1. The results differ somewhat from those described by Staples and Tobeg but agree substantially with those recorded by Taube and L ~ e l i g e r . ~Considerable effort was expended t o test the isomeric purity of the samples, and some of the problems encountered are discussed below. Unfortunately the molar absorptivity a t the maximum for the first absorption band for cis- [Co(en)2N&l]C10* ( E 215) is close to that at the same wavelength for an equimolar mixture of cis-[ C ~ ( e n ) ~ C l ~ ] c104 ( E 85) and cis-[Co(en)2N3)~lC104( E 335). HOWever, the isolated chloroazido complexes were chromatographed on thin layer cellulose with a C4Hg0HHz0-HC104 mixture. This procedure separated all three possible cis species and showed that the (+)[Co(en)2ClN3]C104 samples used in this investigation contained no detectable amounts of dichloro or diazido complexes. Conductance measuremen ts for the aquation of ~is-[Co(en)~ClN~]C104 (2 X M) to the aquoazido complex in perchloric acid ( l O V -If)a t 25' gave a rate constant of 2.6 X lop4 sec-' which is close to the value reported by Staples and Tobe and also to that for the aquation of the cis- [Co(en)zClz]+ion ( k = 2.5 X lop4 sec)lz under the same conditions. For cis[Co(en)~(N3)2]C104the rate constant for the aquation of the first azide ion is too slow to ~ 0 n t r i b u t e . I ~ Clearly the visible spectra and rate of aquation of C1(12) R. G. Pearson, C. R. Boston. and F.Dasolo, .I. P h y s . Chpm., 59, 30.1 (1955). (13) P. 5. Stnplrs, .I. Che?n. .Sot., 745 (106,I).
AZIDOCHLOROBIS (ETHYLENEDIAMINE) COBALT (111) ION 1809
17t71. 6, No. 10, October 1967
cis-aquoazido complex reacted with NO+ to give 1OOyo cis- [ C ~ ( e n ) ~ ( O H ~ in ) z lagreement ~+ with ref 3. The composition of the product mixtures in the reactions described below was calculated from spectrophotometric data using the above molar absorptivities for cis- and trans- [C0(en)~ClN3]+and the following literature values for the other complex ions: trunsIC0 (en)dHzO)21(NO&, E492 19.2 ; cis- [Co(en)~(H20)~ 1(NO&, €492 80.0;14 cis- [ C O ( ~ ~ ) ~ ( H ~ O ) C ~ ] S O ~ ~ ~ H 651j 91; trans-[Co(en)z(H20)Cl]S04, €515 11.2.15 For the molar rotation of ( - ) j ~ [ C o ( e n ) ~ C O ~ ] C0.510~~ H20 [ M I D is -4511' mole-1 cm-1.16 Jnduced Aquations of (+)520- [C0(en)~N~Cl]Cl0~.The Hg2+ ion assisted aquation in dilute HCIO, gave 84 f 2% cis- and 16 2% trans-[C~(en)~(H~O)N~]~+ complex (spectrophotometric values). This mixture when treated with "0.2 gave 88% cis- and 12% truns[Co(en)2(H20)2I3+ (spectrophotometric values). The optical rotation of the carbonato complex formed by treating the diaquo mixture with NaHC03 showed that 81 f 2Oj, of the diaquo product was optically pure ~ ( + ) ~ 8 9 It . has been established elsewhereI6 that D-cis-[Co(en)z(H20)2I3+reacts with HC03- to give D- [ C 0 ( e n ) ~ C 0 ~ ]with + full retention of activity and configuration. Loeliger and Taube3 found that cisI I I 600 500 400 [c o (en)2 (H20)N3] + reacted with nitrous acid withW a v e l e n g t h (Mp) out change in configuration and this conclusion is conFigure 1.-Visible absorption spectra of: - (4 )588-cisfirmed b y the present work. The nitrous acid induced [Co(en)zNd21](ClO&; - - - -, trans-[Co(en)zNaHzO]S04.2H20; aquation of (+)589-[C~(en)2N3C1](C10~) gave 79 f 2% - . - . , cis-[Co(en)zN3H~O]SO4.H20. cis- and 21 f 2y0trans-[Co(en)2(H~O)Cl]~+, and reacdo not allow a characterization of the chloroazido tion of the chloroaquo products with NaHC03 gave species but the initial and final molar conductivities A 79 =t2% ~ ( f ) ~ ~ ~ - [ C o ( e n ) ~ C 0 3 ] + . * ~ compared with those for the reference ions cis- [ C ~ ( e n ) ~ - Induced Aquation of ( +)w[Co(en)2C12]+.-The (NOz)z]C104 (A = 86 ohm-l) and [C~(en)~((-)val)]- Hg2+-induced aquation of (+)w [Co(enj2CL]+ deC1, (A = 194 ohm-l) also showed that the chloroazido scribed in an earlier article2 has been repeated yielding complex was free of the dichloro and diazido complexes. slightly different results. The spectrophotometric For cis- [ C O ( ~ ~ ) IC104 ~ N ~A C was ~ found t o be 85 ohm-l values were 76% cis- and 24% tr~ns-[Co(en)~Cl(OH~) 12+ and for the aquated product A was 198 ohm-l, after corand the polarimetric value was 78y0 D-cis. The disrection for the conductance of the acid. It is clear crepancy between these values and those previously that a mixture of the dichloro and diazido complexes reported (7ooj, cis, 30y0 trans, and 70% D-cis) is would release less than one anion per molecular ion ascribed to the more accurate instruments used in this under the conditions used. In the infrared spectrum study. The differences however do not alter the conof cis- [C0(en)~(N~)~]C104 a doublet appeared for the clusions reached in the previous article. azide N-N stretching mode at 2025 and 2100 cm-l but I t should be noted that Hg2+ does not catalyze the only a singlet appeared a t 2050 cm-l for cis-[Co(en)zisomerization trans- $ cis-[C0(en)~C1OH~ J2+ nor cis $ ClN~lC104. This is also consistent with the conclutrans- [Co(en)&12] +. sion that the complex is not a mixture. Induced Aquation of ( +)58g-cis-[ C O ( ~ ~ ) ~ ( N ~ ) ~ ] C I O ~ . The cis- and trans- [ C O ( ~ ~ ) ~ ( H ~ Ocomplexes ) N ~ ] ~ + The reaction of (+)5sg-cis- [ C 0 ( e n ) ~ ( N ~ ) ~ ] Cwith 10~ were isolated as the sulfates. At 500 mp the molar nitrous acid was studied by Loeliger and T a ~ b ewho ,~ absorptivities were found t o be B 293 for ~is-[Co(en)~- found that the complex reacted to form 77 =F 3y0cis(H20)NB]S04.H20 and E 103 for trans-[Co(en)z(HzO)- and 23 f 3y0 trans-aquoazido complexes, that the cisN3]S04.2Hz0. These results agree with those of aquoazido complex reacts further to give cis-diaquowith Loeliger and Taube3 and confirm their conclusion retention of configuration, and that trans- [ C ~ ( e n ) ~ that the separation of the two isomers prepared by (HzO)N3]2+reacts to give 40 =t 5% cis-diaquo comStaples and Tobe was incomplete. Optically implex. By repeating these reactions and using the pure cis- [Co(en)2(H2O)Ns]SOa was prepared from the molar absorptivities of the prepared cis- and trans(+)- [Co(en)zC1N3I2+ ion. Some racemization oc[C0(en)z(H20)N3]~+complexes, we found that in the curred during the preparation, and the solubility differ(14) J. B j e r r u m a n d S. E. Rasmussen, Acta Chem. S c a d , 6 , 1265 (1952). ( 1 5 ) A. M. Sargeson, A u s t d i ~ nJ. Chem., 16, 352 (1963). ence between the active and racemic isomers was too (16) F. P. Dwyer, A. M. Sargeson, a n d I. K. Reid, J . Am. Chem. Soc., 811, small to effect a sharp fractionation. However, the 1215 (1'263).
*
I
11. A. BUCICINGHAM, I I. OLSEN,ANI, A. XT. SARCESON
ISIO
p!
2
2 1.0
.-c0 0
c
0
M
c
0 -
2
- 1.0
show not only that there is full retention of the geometrical configuration which is consistent with the conclusion of Staples and Tobe, but also that there is full retention of the D ( + ) configuration. It is necessary to establish the latter fact since it is conceivable that a D - C ~ Sreactant could give both D- and L-cis products. The configurational relationship between (+)6s9[Co(en)2C1N3]+, (+)w [Co(en)2(N3)?]+,and the reaction products was deduced from the circular dichroism,l8 the rotatory dispersion curves,Ig and previous structural?Oand chemicallgstudies. The isomerization results for cis- [ C O ( ~ ~ ) ~ ( H , O ) N ~ ] SO4 differ slightly from those of Staples and Tobe," who found a rate constant KI k-I = 1.0 X sec-I and an equilibrium mixture of 73% cis- and 27% trans[Co(en)z(H20)N3](ClO&. This ratio adjusts to 57y0 cis and 43y0 trans if the present values for the molar absorptivities of the aquoazido ions are used. Spontaneous Aquation of ( +)jSg- [Co(en)2C12]C104.-The course of aquation of (+)589-[C0(en)~Cl~]+ was established by allowing the dichloro ion to aquate to the chloroaquo species (5tl;.?) which was then converted mith NaHC03 to the active carbonato complex. The degree of retention observed after allowance had been made for the subsequent isomerization of the cischloroaquo isomer showed that the dichloro aquated with retention (100 27,) of the D-cis configuration. A similar result was obtained by extrapolating the plot of log a0 us. t for the racemization of the D-cischloroaquo ion obtained above to zero time \Thence the extrapolated rotation agreed with that for optically pure D- [C0(en)~C10H~]Br~. 2Hz0. The catalyzed aquations in the presence of mercuric ions and nitrous acid are rapid by comparison with the subsequent isomerization and aquation reactions of the a z i d ~ a q u o , ' the ~ chloroaquo,15 and the dia ~ p complexes. o ~ ~ All measurements were performed immediately after completion of the reactions and i t was possible in all cases to measure the composition of the product mixtures before further aquation or isomerization became significant, so that there was no doubt that the observed product distributions were due to the induced aquatior!s and not complicated by further reactions. A summary of the steric course of the aquation reactions is presented in Scheme I.
+
- 21) I
SA0
600
W a v e l e n g t h (MP)
Figure
Tnovgcinic Chemislry
-Rotary
dispersion curves for ( f )ss9-cis-[Co(en)dYBC1] (2104.
first step 84 f 2% cis- and 16 f 2% trans-aquoazido was formed and that this mixture reacted with another equivalent of nitrous acid to give 90 =t 2% cis-diaquo of which 82 f 2% by conversion to the carbonato complex was shown to be optically active. The amounts of trans-aquoazido and trans-diaquo complexes formed were too small to allow a reliable estimation of the concentration of these complexes but qualitatively the results agree with those of Loeliger and T a ~ b e . ~ Spontaneous Aquation of ( +)6ss-cis- [Co(en),N,Cl]C104.-The release of the chloride ion from (+)js9-cis[C0(en)~N~Cl]C104 was followed conductometrically in lov3 M perchloric acid a t 25'. A plot of log (A, A,) against time where A, and A, are the measured conductances at t = m andt, respectively, gaveastraight line. The first-order rate constant was calculated to be 2.6 X sec-I in reasonable agreement with Staples and Tobe's result1' (2.4 X loF4 sec-l at 2 5 O , M HClO4). In order to determine the steric course of the reaction, the rate of isomerization of cis- [Co(en)2(H2O)N3I2 and the equilibrium composition were remeasured.l' From the rotation of the carbonato coniDiscussion plex formed after the nitrosation of the aquoazido The induced aquations are rapid, are effected by reaquation product, the amount of active cis- [Co(en)%agents which lead to good leaving groups at the cobalt(H20)N3I2+was calculated. The isomerization studies (111) center, and are therefore conducive to the proof the cis-aquoazido complex in l o p 2 M perchloric acid duction of intermediates of reduced coordination nunia t 25' showed that isomerization took place with a ber. These considerations, coupled n-ith isotope fracfirst-order rate constant kl k-1 = 1.4 X sec-l tionation, competition studies, and stereochemical and gave an equilibrium concentration of 58 i= 2% evidence from the induced aquations for the cobalt(II1) cis- and 42 =F 2y0 trans-[C~(en)~(H~O)N~]SO~. From pentaammine c ~ m p l e x e s , ~suggest -~ that five-coordithese data and the rate constant for the aquation of cisnate intermediates are likely. With these factors in [C0(en)~N~Cl]C10~ (2.6 X sec-I), the spontaneous aquation of the optically active chloroazido complex (18) A. J. McCaffery, S.F. Mason, and B. J. h-orman, ibid., 6094 (1966). was calculated to have occurred with 100 i. 2% reten(19) T. E. MiIacDermott a n d A. M. Sargesun, Az~slralznnJ . Chrm., 16, :3B-L (1963). tion of cis configuration and activity. These results
*
f
+
(17) P. J. Staples and \I L Tobe, J . Chenz. Soc , 4805 (1960).
(20) G. A. Barclay, E. Goldschmeid, N. C . Stepiiensoii, and A . IN.S a t p son, C h m . Coininirii., RtO ( I O K l i ) .
AZIDOCHLOROBIS(ETHYLENEDIAMINE)COBALT(~~~) ION 1811
Vol. 6 , No. 10, October 1967
SCHEME I STEKIC
COURSE OF THE
INDUCED
Hg’’ I)(
+)88(,-
[ C ~ ( e i i ) ~ N ~+ C .l] f (+)5~~-[Co(enjr(HzO)nT3] 2f 84 k 270
.1
HNOz
(
+
)BO-[ Co (en )Z
(HzO)z]
AQUATIONS
+ tuans-[Co(eii)~(H~O)r\‘~] 2i-
16 F 2%
.1
HNOa
+
dl- [ Co (en )z(HzO)Z]
+
+ ti,ans- [ Co en)^ (HzO)z]
3+
experimental error to wai-rant more than the statemind the results are arranged to show the amounts of czs- and trans- [ C o ( e n ) ~ C 1 0 H ~or ] ~-+[Co(en)~OH~N31~+ment that they agree qualitatively with the more precise results of Loeliger and Taube3 for this reaction. derived from the different reactions. It is clear from The steric course for the spontaneous aquation for the data in Scheme I that cis-[Co(en)2Clz]f Hg2+ D- [Co(en)zClZ]+and D- [Co(en)zClN3]+occurs with full and c i s - [ C ~ ( e n ) ~ N ~ C l NO+ ] + give a common chlororetention (100 It 2%) of the D-cis configuration. The aquo product and that cis-[Co(en)z(N3)2]+ NO+ azidoaquo and chloroaquo products subsequently and cis- [Co(en)zClN3]+ Hg2+ give a common aquoisomerize. However, the steric courses of the induced azido product within the experimental error. These aquations differ widely from those for the correspondresults fit the general pattern outlined by Taube and ing spontaneous aquations and are consistent with the Loeliger in Table I V of ref 4 and are consistent with the production of a trigonal bipyramid of the form of I, production of a five-coordinate intermediate. The results are meaningful since appreciable amounts of both cis and trans isomers are produced from the cis reactants. When little rearrangement occurs, the distinction between 99% cis and 99.9% cis product is difficult to ascertain and no clear decision can be made about the steric course of the reactions4 The results I are sufficiently accurate to allow conclusions to be which reacts with the solvent in the trigonal plane and drawn about the existence of the [Co(en)2C1l2+and which shows some dependence for the product ratio [Co(en)~N3]~+ intermediates, but they do not permit on the nature of X, where X = C1, N3, or HzO. The any conclusions concerning the existence of the possible D- [Co(en)20H2]3+intermediate reacts with full reten[Co(en)zHzO]+ intermediate derived from the nitrosation of the cis-D configuration4 whereas [ C ~ ( e n ) ~ C l ] ~ + tion of the trans- [ C O ( ~ ~ ) ~ N ~ by-product. O H ~ ] ~ + The and [ c ~ ( e n ) ~ Ngive ~ ] ~both + cis and trans isomers in amounts of cis- and trans- [ C O ( ~ ~ ) ~ ( O H , formed ),]~+ similar amounts. Also it seems that there is some preffrom this source are not sufficiently different from the
+ +
+ +
1812 A. CHAKRAVORTY
AND
B. BEHERA
Inorganic Chemistry
erence, over the statistical values, for reaction in the positions cis to the substituent and this may be associated with the ability of the incoming solvent molecule to hydrogen bond 17-iththe electronegative substituent. The cis product in each instance is optically pure ( 5 2 % ) and this excludes any appreciable amount of the alternative form of the trigonal bipyramid. The results may be contrasted with those obtained for the induced aquations of trans- [Co(NH3)4(ND3)N3I2+ and t~ans-[Co(NH~)1(ND~)Xl~+~ (X = C1, Br) where no rearrangement 17-asobserved. The difference between the two sets of data may result from the possible stabilization of the trigonal bipyramid in the [Co(en)lX] system by bonding the filled p orbitals of appropriate symmetry on the substituent to the vacated cobalt orbital as suggested by Basolo and Pearson.21 This possibility does not arise when X = NH3 so that to be consistent with this proposal full retention of configuration should be observed in the induced aqua-
tions of cis- [Co(en)2NH3r\r3I2+and cis- [Co(en)&H3C1I2+. These systems are at present being examined. Also initial studies show that full retention of configuration occurs in the analogous reactions of the [Co(tetraethylenepentamine)XI2+ isomers (X = N3, C1, Br).22 It seems unlikely that these and previous results2can be explained by coincidences in the reactivity pattern for the reaction intermediates RCoNNN03+ and RCoC1Hg4+ over a range of complexes and for several methods of detecting their behavior. It is more logical to argue that the common results obtained for the isotopic fractionation factor, the competition studies, and the stereochemistry of the products for the sets of complexes are explained by a common cause, rather than by multiple coincidences.
(21) F. Basolo and R. G. Pearson, “hlechanisms of Inorganic Reactions,” John Wiley a n d Sons, Inc., New York, K,Y . , 1958, p 133.
(22) D. A. Buckingham, P. A. hIarzilli, and A. LI. Sargeson, t o be published.
Acknowledgment.-The authors thank the Microanalytical Unit of the John Curtin School of Medical Research for the C, H , and N microanalyses.
CONTRIBUTIOS FROM THE LNDIAS INSTITUTE O F
DEPARTMENT O F CHEMISTRY, TECHNOLOGY, KASPUR,I N D I A
Synthesis, Nuclear Resonance, and Electronic Spectra of Tris(2-hydroxypropiophenimine)cobalt(III) BY A. CHAKRAYORTY AND B. BEHERA
IieLeived June 5, 1967 Several tris(N-alkyl-2-liydrogyprol?ioplicliciiir~iiii~)co~~lt(III) cornpoutids have been sytlthesized by a notiaqueous chelatiotl exists as a 1 : 1 dichlorometharie adduct in which dichlororeaction. Tris(N-methy1-2-hydroxypropiophenimine)cobalt(III) methane is held very strongly in the crystal lattice. The chelates exist exclusively in the trans form. The aromatic region of the nuclear resonance spectra of the chelates is discussed in some detail, and it is shown that definite assignments can be made for several signals. The crystal field spectra of the chelates are compatible with an essentially octahedral field having a rhombic component. This component clearly splits the ‘AI,-+ ‘TI, transition in some cases. A shoulder around 24,000 cm-’ presumably represents the lAi, -+ l T p g transition
Introduction As part of our general program1,2on the studies of transition metal complexes derived from ligands of type 1, me recently reported the nuclear resonance and crystal field spectra of 2-hydroxyacetophenirninechelates of trivalent cobalt1 (3, R = alkyl, X = H) These complexes belong to the class CO(A-B)~where h-B is a n
1
2, R‘=H
3, R’ = CH3 4, R’= C,H, (1) A. Chakravorty a n d K. C. Kalia, I n o l g Chain., 6 , 690 (1967). (2) A. Chakravorty, T. S. K a n n a n , and S . G u p t a , copper and nickel complexes of 1 (R’ = CHa), to be published.
unsymmetrical bidentate ligand. The trans geometry of 2 and 3 was demonstrated unequivocally by proton resonance spectra.lg3 I n the present paper we report the synthesis, nuclear resonance, and electronic spectra of the corresponding 2-hydroxypropiophenimine chelates 4 (R = alkyl, X = H or 5-CH3). Synthesis of 3 required a nonaqueous chelation reaction in most cases. The same is found to be true for 4, as one might intuitively expect. The salicylaldimines, 2, can, on the other hand, be made in general by aqueous chelati~n.~~* The nuclear resonance spectra of 4 both in alkyl and aromatic regions are compatible only with the expected trans structure. T o facilitate analysis of the spectrum in the aromatic region in detail, complex 3 (R = CH3, X = 4,5-(CH3)%) was synthesized. (3) A. Chakravorty a n d R. H. Holm, Iizovg. Chem., 3 , 1621 (1964). (4) B. 0 . West, J . Chem. SOL,4944 (1960).
